1. Field of the Invention
The present invention relates to a novel and efficient system for preventing the entry of ground moisture into so-called crawlspaces of buildings such as homes, and for permitting the free drainage of groundwater from the floor thereof, whether dirt or concrete. Moisture is very damaging to wood structural support members of buildings and is absorbed by such members from the ground and from moist air in contact therewith.
As disclosed in my U.S. Pat. No. 6,575,661, issued Jun. 10, 2003, the disclosure of which is hereby incorporated herein, many buildings and homes are built without basements, and are elevated a few feet above the ground on support members such as stone, poured concrete or concrete block walls. In many cases the crawlspace between the ground surface and the wooden floor beams or joists of the house is at a level below the level of the surrounding soil, or below the level of saturated soils in wet weather, so that water flows into and is absorbed up through the floor of the crawlspace, usually a dirt surface, from adjacent ground areas of higher elevation and up from the sub-soil. Such water is drawn into the headroom of the crawl space in the form of water vapor and penetrates the wooden structural members of the building, causing wood rot, mold, odors, attraction of ants and other insects, rodents etc. Also, the escape of dangerous radon gas from the ground into the crawlspace and into the building is another problem.
Even in crawlspaces that do not leak or flood from groundwater, the earth below the crawlspace, and forming the floor of the crawlspace, has a high humidity level most of the time, and this water vapor rises into the crawlspace to produce a humid air atmosphere within the crawlspace, which moves upwardly to penetrate the structural framing and living spaces above the crawlspace.
Mold spores exist in air and grow into destructive mold in the presence of organic material, such as moist wood. Humidity levels of from 50% to 90% are common in crawlspaces, even those that have never flooded. Mold can grow on dirt, insulation, wood framing and even under carpeting on the floor within the home. Mold digests and destroys organic materials as it feeds on them. Damp environments also provide an inviting environment for insects such as termites, ants and other insects which feed on moist organic material such as structural support wood and can contribute to the destruction and collapse thereof.
2. State of the Art
In an effort to prevent the penetration of water and water vapor into building crawlspaces it has been proposed to apply a continuous moisture barrier layer such as a 6 mil thick plastic film over the dirt floor of the crawlspace. This has been proven to be unsatisfactory, per se, since water is drawn up from the ground, beneath the barrier, and leaks and/or vaporizes around the edges of the barrier into the crawlspace environment. Also, ground water penetrates the walls of the crawlspace and/or otherwise enters the crawlspace and accumulates on top of the vapor barrier film and generates moisture which permeates into the wooden structural supports of the building resulting in rot and decay, mold and fungus, odors and vermin. Also a 6 mil vapor barrier film is not sufficiently durable to resist tearing and being punctured under the stress and weight of a workman crawling on it.
U.S. Pat. No. 5,642,967 discloses a system in which the barrier film is associated with an excavated pit filled with aggregate.
Water entering the crawlspace collects in the pit and is pumped from a sump when necessary. A vapor barrier film is applied over the dirt floor of the crawlspace, and over the pit and sump areas, to prevent moisture from entering the building. Such a system is unsatisfactory because it has no means for preventing the entry of ground water and its accumulation on the surface of the barrier film, with the disadvantages discussed supra.
U.S. Pat. No. 5,890,845 discloses another system in which the dirt floor of a crawlspace is covered with a layer of lightweight concrete material applied over a plastic film barrier layer. While the barrier layer blocks the penetration of moisture from the ground up into the crawlspace, the system provides no means for preventing the entry of ground water through the walls of the crawlspace onto the surface of the concrete material where it can accumulate in surface depressions and develop moisture, with the disadvantages discussed supra.
My aforementioned U.S. Pat. No. 6,575,666 discloses a system which prevents the entry of water from the sub-soil and also from higher elevations of the surrounding ground, such as excessive ground water caused by rain, snow and/or flooding, into crawlspaces directly or through concrete block walls which surround and enclose the crawlspace. The system of U.S. Pat. No. 6,575,666 comprises applying over the floor of the crawlspace, generally a dirt floor but sometimes a poured concrete floor, a continuous sealed plastic film barrier layer, and extending the barrier film vertically-upwardly to cover and seal the interior peripheral walls enclosing the crawlspace to an elevation at least slightly greater than the elevation of the ground in contact with the exterior surfaces of the peripheral walls and preferably to the tops of the peripheral walls. This encapsulates the dirt surface of the entire crawlspace against the penetration of external ground water or flood water and also sub-soil water and water vapor onto the surface of the plastic barrier film and into the crawlspace atmosphere.
According to an embodiment of U.S. Pat. No. 6,575,666, the dirt surface of the crawlspace may be first provided with a sump pit and/or a drainage trench system for the collection of sub-soil water that leaks in from the crawlspace floor or walls under the barrier layer. A perimeter drain conduit or sump pump may be associated with the sump pit or drainage trench, depending upon the degree of wetness of the crawlspace and the grade and elevation of the exterior ground surrounding the floor of the crawlspace, to discharge excessive amounts of water accumulated beneath the barrier layer to areas exterior to the crawl space.
In situations involving a pre-existing crawlspace having a dirt floor or a concrete floor with a water leakage problem and no peripheral water drainage system or drainage trench, it is generally not possible, because of the head space limitations, to dig a suitable perimeter drainage trench in a dirt floor, or to jackhammer a suitable peripheral trench or sump pit, through a concrete floor, and to install a heavy drainage stone bed under the vapor barrier liner to enable water drainage from beneath the liner. In such situations there is a need for a compact, lightweight alternative system which is easy to install over the dirt or concrete floor of a crawlspace, in place of or beneath a durable vapor barrier liner, to enable and facilitate the drainage of water from, the surface of the dirt or concrete floor to a low spot such as a sump pit.
While the system of U.S. Pat. No. 6,575,666 represents a substantial improvement in the waterproofing of crawlspaces, there remains a need for an improved system which avoids the trapping and pudding of ground water beneath the barrier layer, especially over a concrete floor of the crawlspace, and which further insulates the barrier layer against rough concrete surfaces rupturing or tearing the membrane under the weight of workmen crawling thereover during installation or at other times.